| Abstract: |
The high frequency pulse detonation (HFPD) process has shown to be a cost effective spray technique able to produce dense and well bonded metal, cermet and oxide coatings with the best technical and functional performances. Due to the lack of mechanical moving parts, the HFPD system can be operated in a wide range of explosion frequencies (up to more than 100 Hz) and gas mixtures, thus allowing the processing of a wide spectrum of feedstock materials with the high particle velocities characteristic for detonation spraying. This work deals with the development of dense and high quality Ni- and Co-based coatings by means of the HFPD techquine. During this development, the gun configuration and the process parameters (gas flows, explosion frequency, spray distance and kinetic conditions) have been optimised to obtain dense coatings, with a high coating/substrate bonding strength and low oxygen content. The oxidation behavior of the optimised coatings has been investigated under isothermal oxidation at 900ºC and 1.100ºC for different times. The cross-sectional microstructure of the coatings has been studied as-sprayed as well as following heat-treatment by optical and scanning electron microscopy. Moreover, the oxidation behavior of the coatings has been characterized through the surface morphology and microstructure of the oxide scales by scanning electron microscopy and X-ray diffraction analysis.
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